DNA damage caused by radiation though causes stress to the body of any organism and they have to invest a lot of energy repairing that damage everyday.

Are you confusing the two things? Or are you just not clear on evolutionary process?

Genetic mutation as in mutations which bring about variation in a population can be beneficial or detrimental.

Quoting: Aucuparia

Tell me of one example of e genetic mutation that was caused by radiation that resulted in a beneficial adaptation in any creature or living thing. You have the whole internet right in fornt of you, you ought to be able to come up with at least a single example. YOU CANNOT. When dna is damaged by ionization radiation the result is either death of the cell or reproduction of useless cells.. Are you aware of the experimentation done in this area of study?There has yet to be ones such example in all of this experimentation.

There is a normal variation of genetic dna sequences in all living things that is not the result of damage, and beneficial variations tend to survive in greater numbers than their contemporaries. This is the mechanism of evolution.